The present invention relates generally to test systems and methods, and in particular, to test systems and methods used in testing devices having circuit and ground connections for receiving power from external sources.
Devices that derive electrical power from external sources, such as utility power, typically include a circuit connection and a ground connection for connecting to the external power source. Such devices include, among other things, consumer appliances, industrial equipment, and computer equipment. The circuit connection in such devices generally includes two contact points across which the device is connected to complete the power circuit. The ground connection in the device is intended to be connected to a electrical ground. According to many international safety standards, the ground connection must also electrically connect the metal chassis of the device to electrical ground.
Several international standards define tests relating to the electrical interconnection and/or isolation of the circuit connection, the ground connection, and the metal chassis of an electrical device. Such test are referred to herein as electrical safety compliance tests. Two common electrical safety compliance tests are those generally referred to as the dielectric withstand test, and the ground continuity test. Electrical devices must typically pass such tests before being sold commercially.
The dielectric withstand test measures the isolation between the circuit connection and the ground connection at high voltages. To this end, a high voltage typically exceeding 1000 volts AC or DC is applied across the circuit connection and the ground connection of the device. The current is then measured. If the current exceeds a maximum allowable current threshold, the isolation between circuit and ground connection of the device is considered to be insufficient. If the isolation between the circuit and ground connection is insufficient, high voltages may propagate to the metal chassis during operation of the device, thereby creating a potential safety hazard.
The ground continuity test measures the resistance between the ground connection and the device chassis. The ground continuity test assures that the metal chassis will be electrically grounded during normal operation of the device. If a high resistance is detected, the chassis may not be properly grounded, thereby creating a potential shock hazard.
One problem associated with performing the dielectric withstand test and the ground continuity test is that many countries have unique test requirements. While the type of tests are generally the same from country to country, the specific test parameters vary. For example, the U.S. standards body, UL, defines two alternative dielectric withstand tests. One UL dielectric withstand test requires that a product be able to withstand application of 1500 volts AC for one minute. Another UL dielectric withstand test requires that a device be able to withstand application of 1725 volts DC for one second. By contrast, the United Kingdom standards body, BABT, requires that a device be able to withstand 2800 volts AC for one minute or 2125 volts DC for one second. Still other standards, such as the CSA standard of Canada, require devices to withstand other levels of voltage for particular time increments. Specific parameters associated with the ground continuity test also vary among the different nations"" standards.
Accordingly, in a manufacturing environment where different products are intended for export to different countries, testing a product for electrical safety compliance requires a labor intensive procedure of obtaining the applicable international standard, obtaining the test parameters associated with the applicable international standard, and performing the test on the device using the appropriate test parameters. Moreover, the test data must be recorded and associated with the device under test. Such activities are not only labor intensive, but furthermore require highly skilled operators who are knowledgeable about the products, their international markets, and the standards of various countries.
To assist in carrying out dielectric withstand tests and ground continuity tests, a dielectric tester known as the VITREK 944i Dielectric Analyzer has been developed, which is available from Vitrek Corporation of San Diego, Calif. The VITREK 944i Dielectric Analyzer (hereinafter xe2x80x9cVitrek Analyzerxe2x80x9d) performs AC and DC dielectric tests, ground continuity tests and other tests, based on input test parameters.
To alleviate the need for providing test parameters for each operation of a test, the Vitrek Analyzer allows a user to store up to ninety-nine test programs. To perform a particular test, the operator may select the appropriate one of the stored test programs through the keypad on the Vitrek Analyzer.
The Vitrek Analyzer also includes the ability to communicate with external devices, such as a general purpose computer. As discussed in the Vitrek 944i Dielectric Analyzer Operating and Maintenance Manual (Vitrek Corporation, 1994) (hereinafter xe2x80x9cVitrek Manualxe2x80x9d), which is incorporated herein by reference, the Vitrek Analyzer allows individual tests to be configured and executed through an external communication link. In particular, the Vitrek Manual teaches that individual single step tests may be configured at a general purpose computer and then communicated to the Vitrek Analyzer. The Vitrek Manual also teaches that the Vitrek Analyzer may communicate test results over the communication link to an external device, such as general purpose computer.
While the Vitrek Analyzer provides a valuable tool for performing electrical safety compliance tests, the Vitrek Analyzer nevertheless has shortcomings. First, the user interface capabilities of the Vitrek Analyzer are limited. In particular, the stored test programs may only be accessed through the Vitrek Analyzer keypad by their two digit number. Thus, for example, if an operator stores several test programs in the Vitrek Analyzer, the operator must memorize or record on paper which test standard is associated with each stored test""s two digit identification number. Moreover, the test programs stored in the Vitrek Analyzer may not be accessed through the communication link, or in other words, by an external computer. Thus, if the test programs stored in the Vitrek Analyzer are to be accessed, they must be accessed through operator input at the front panel of the Vitrek Analyzer, which, as discussed above, has extremely limited user interface capabilities.
Moreover, the Vitrek Manual does not teach a fully automated test system that is capable of performing tests that conform to the various nations"" electrical safety compliance standards in an intuitive and straightforward manner. There is a need, therefore, for a fully automated test system that performs one of a plurality of electrical safety compliance tests with reduced labor effort and knowledge than that required by conventional test systems, including those taught by the Vitrek Manual. There is a further need for such a fully automated test system that is menu-driven, thereby reducing the complexity of operation of the system. There is yet a further need for a system that automatically obtains tracking identification data associated with each test performed by the automated test system.
The present invention fulfills the above needs, as well as others, by providing a test system that and method that allows an operator to select one of a plurality of product model identifiers through a user interface and cause a test apparatus, for example, the Vitrek Analyzer, to perform appropriate tests based on the operator selection. In other words, the operator merely identifies the type of product being tested, and the test system and method of the present invention automatically performs the appropriate tests. Accordingly, the operator need not know the particular test parameters or even the appropriate international standard to be applied. The ability to perform appropriate tests in an automated manner based on a selection of a product model identifier thus provides a highly automated, intuitive electrical safety compliance testing device.
In one embodiment, the present invention is an automated test system for testing a device that has a circuit connection and a ground connection. The automated test system includes a storage device, an input device, a processor, and a test apparatus. The storage device is operable to store a plurality of sets of test parameters, and is further operable to store a plurality of product model identifiers, each product model identifier associated with one of the plurality of sets of test parameters. The input device is operable to obtain input from an operator defining a first product model identifier from the plurality of product model identifiers. The processor is coupled to the input device and the storage device and is operable to receive the input from the input device and retrieve the set of test parameters associated with the first product model identifier from the storage device based on the input. The processor is further operable to generate a control signal that includes the retrieved set of test parameters. The test apparatus includes a first connection operable to be connected to the circuit connection of the device and a second connection operable to be connected to the ground connection of the device. The test apparatus is further operably connected to receive the control signal including the retrieved set of test parameters from the processor. The test apparatus is operable to perform a first test based on the first set of test parameters.
The use of the external processor, memory and user interface provides extensive user-interface and interconnection capabilities not found within the test apparatus itself. The automation and interconnection capabilities combined with the ability to select one of a plurality of test standards from the external user interface reduces the level of expertise require to perform the safety compliance tests as compared to the test systems taught by the prior art.
The above features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings.